Well bit



July 10, 1934- J. H. HdWARD ET AL WELL BIT Filed Sept. 14, 1932 3 Sheets-Sheet l d 0 W/ MM w 25 y w 3% #w @W ojW/v a v 3 1/1 fa g a? w w 6 w m a July 10, 1934., J. H. HOWARD El AL 1,966,345

' WELL BIT Filed Sept. 14, 1932 5 Sheets-Sheet 2 and Patented July 10, 1934 UNITED. STATES 1,966,346 PATENT OFFICE 1,966,346 'WELL arr John 11. Howard, Huntington Park, and Alfred C. Catland, Alhambra, Calif., assignora to Globe Oil Tools Company, Los Nietos, cum, a corporation of California Application September 14, 1932, Serial No. 633,062

12 Claims. (Cl. 255-71) troduced have structural characteristics that place marked limitations on their effectiveness and speed of operation or penetration of the earth formation. 'It is recognized as desirable to employ roller cutters whose cutting parts or teeth are formed and spaced so that there is a minimum total lineal cutting edge acting on the formation at one time to provide for a maximum pressure per each active lineal unit of the cutting edge, and therefore provide for a more effective and rapid penetration of the earth formation. The total average lineal cutting edge acting on the formation may be lessened by increasing the spacing of the adjacent teeth of the roller cutter, but

if the spacing or circular pitch of the cutting edge of the teeth is too great, the roller cutter skids or drags over the formation without rotating.

that is particularly effective and rapid in its cutting action.

It isanother object of the invention to provide a well bit including a roller cutter unit involving two or more circumferential sets of spaced cutting parts' or teeth, the teeth of the adjacent sets or series being staggered or offset. The teeth of the sets or series above mentioned may be spaced apart considerable distances as the teeth of one series supplement or follow the teethof another set in their action on the formation so that there is never a large toothless gap occurring at the point of engagement of the cutter with the formation. Due to this offset relationship of the teeth in the several adjacent series, a minimum average lineal cutting edge acts on the formation to provide for a very effective and speedy cutting action.

It is another object of the invention to provide a roller cutter for use on a well tool in which the cutting parts or teeth do not track in the cuts or notches they have made in the formation during a previous rotationof the cutter or bit. In accordance with the present invention, the teeth of each series or set of teeth of the roller cutter have different or varied spacing and therefore cannot track in their cuts.

It is another object of the invention to provide Thespacing of the cutting parts or teeth of a roller cutter is therefore limited, and accordingly the a roller well bit in which the cutters are mounted or positioned with respect to one another to provide for the effective drilling of a round, true or vertical bore. In the bit provided by the present invention, an inner cutting means cuts a round central opening in the formation and two or more outer cutters overlap one another in their action on the formation to make an annular cut around and joining the opening made by the inner cutter.

It is another object of the invention to provide a well bit of the character mentioned that embodies a removable integral or one piece bearing member for carrying the several cutters, that is removably attached to the shank of the tool in a simple and effective manner.

It is another object of the invention to provide a roller bit of the character mentioned in which the assembly of the spider or integral mounting member and the several cutters may be easily and quickly attached to and removed from the shank as a unit.

It is another object of the invention toprovide a 'roller bit of the character mentioned that provides for the downward discharge of circulation fluid from the principal means for removably securing the assembly f of ,the mounting member and the cutters to the shank.

It is another object of the invention to provide a roller bit of the character mentioned in which the general construction is simple and sturdy, and that is inexpensive of manufacture.

Other objects and features of the invention' will be best and more fully understood from the following detailed description of typical forms and applications of the invention, throughout which description, reference is had to the accompanying drawings, in which:

Fig.1 is a side elevation of one embodiment of the present invention illustrating it attached to the lower end of a typical drilling string andoperating within a wellbore. Fig. 2 is an enlarged vertical detailed sectional view of the form of bit illustrated in Fi 1.

cated by line 3-3 on Fig. 2. Fi 4 is a bottom elevation of the tool, being a view taken as indicated by line 4-4 on. Fig. 3. Fig. 5 is an enlarged top or plan view of the spider or cutter mounting member. Fig. 6 is a bottom elevation of the shank with the assembly of the spider and cutters removed. Fig. 7 is an enlarged perspective view of one of the cutting units embodied in the tool. Fig. 8 is an end view of another form of cutting unit or cutter. Fig. 9 is a top or' plan view of the cutter illustrated in Fig. 8. Fig. 10 is a bottom plan view of another embodiment of the invention, and Fig. 11 is a vertical detailed sectional view of the principal portion of the tool illustrated in Fig. 10, being a view taken as indicated by line 11-11 on Fig. 10.

Fig. 3 is a central longitudinal detailed sectional view taken as indi-' The roller bit illustrated in Figs. 1 to 7 inclusive of the drawings, includes, generally, a body or shank 10, a cutter carrying member or spider 11 detachably mounted on the lower end of the shank 10, an inner cutting means 12 on the spider 11 for making a round or cylindrical central cut in the formation, an intermediate cutter 13 carried by the spider 11 operable to make an annular out surrounding the cut made by the means 12, and outer cutters 14 for reaming the well bore and for making an annular out which may overlap or join the out made by the intermediate cutter 13.

Thebody orshank 10 is preferably asimple onepiece structure shaped at its lower end to carry the spider 11 and to receive the various cutters, and provided at its upper end with means for connection with a drilling string. In the particular case illustrated, the main or upper portion 16 of the body is cylindrical and is provided at its upper end with a tapered pin 17 screw-threaded into a socket 18 in a typical drill collar 19. A

central longitudinal fluid passage 20 is provided in the shank 10. The main circulation opening 20 terminates at a point above'the lower end of the shank 10 and its lower end portion is enlarged or chambered as at 21.

Two diametrically opposite legs 22 project downwardly from the lower end of the shank 10. The legs 22 may be alike or identical and project outwardly and downwardly from an outwardly and downwardly tapered portion 23 of the shank. The inner sides 24 of the legs 22 are inclined downwardly and outwardly. Pockets or sockets 25 are provided in the inner sides 24 of the legs 23. The sockets 25 extend upwardly from the lower ends of the legs 22 and have flat parallel side walls connected at their upper ends by a continuous curved wall. Inwardly projecting bearing bosses 30 are provided on the inner side 24 of the legs 22 around the sockets 25.

The shank 10 is provided at its lower end with a downwardly projecting leg 26 spaced substantially 90 between the legs 22. The leg 26 projects downwardly from the enlarged or tapered portion 16 of the shank. The inner side 27 of the leg 26 is fiat and substantially vertical. A socket 28 is provided in the inner side 27 of the leg 26. ,The socket 28 extends upwardly from the lower end of the leg 26 and has vertical side walls joined at their upper ends by a continuous curved wall portion. A raised or inwardly projecting bearing boss 29 is provided on the inner side 27 of the leg 26 around the socket 28.

The shank 10 is provided at its lower end with an integral pin 31. The pin 31 projects downwardly from the lower end of the shank 10 and is oifset from the central axis of the, shank, being substantially diametrically opposite the leg 26. The pin 31 projects downwardly from a fiat downwardly facing shoulder 32 on the lower end of the shank.

A spider 11 is provided to carry the several cutters embodied in the bit and is removably attached to the lower end of the shank 10.

It is a feature of the invention that the cutter carrying spider 11 is an integral member formed of a single piece of stock or material. 11 includes a central portion or hub 36 having a vertical opening 33 for receiving the pin 31, and having a flat upper end adapted to seat or bear against the shoulder 32. The lower end of the opening 33 is enlarged orprovided with a socket 34. A nut 35 is threaded on tffie pin 31 and fits the socket 34. The upper end of the nut .35 en- The spider reeaeae gages the bottom of the socket 34 to maintain the upper end of the hub 36 in bearing engagement with the shoulder 32.

In accordance with the invention, a circulation opening 37 extends downwardly through the shank 10 from the chamber 21 and terminates at the lower end of the pin 31. In the particular embodiment of the invention being described, the nut 35 has an extension 38 at its lower end, projecting downwardly beyond the pin 31. The nut extension 38 is tubular and polygonal and is in the nature of a choke or nozzle for the discharge end of the circulation passage 37. In accordance with the broader aspects of the invention, the nozzle or choke for the fluid passage 37 may be a part separable from the nut 35, or may be embodied in the pin 31. A look pin 39 cooperates with registering notches or openings in the nut 35 and spider hub 36 to lock the nut in position.

The bearing member or spider 11 is provided with projecting parts for carrying the cutting means 12 and the cutters 13 and 14. Integral arms 40 project from opposite sides of the hub 36 and are provided at their outer ends with cutter carrying projections 41. The cutter carrying projections 41 are integral with the arms 40 and are provided to carry the outer cutters 14. The projections 41 are inclined upwardly and outwardly as clearly illustrated in Figs. 2 and 5 of the drawings. As integral thrust flange 42 is provided at the inner end of each inclined cutter carrying projection 41. The outer end portions of the projections 41 may be reduced in diameter and fit into and cooperate with the sockets 25 on the inner sides of the legs 22. The projections 41 bridge the spaces between the hub 36 of the spider and the legs 22 and are supported at their opposite ends, thereby constituting arbors for carrying the outer cutters 14. Screws 43 extend through openings in the legs 22 and are threaded into openings 44 in the outer ends of the cutter carrying arbors 41 to aid in detachably securing the spider 11 to the shank 10. The heads of the screws 43 may be counter-sunk in sockets 45 in the outer sides of the legs 22.

A comparatively long projection 46 is provided on the hub 36 of the spider 11 to carry the inner cutting means 12. The cutter carrying projection 46 projects horizontally outward from the hub 36 and is at substantially to the vertical plane in which the axes of the two projections or arbors 41 lie. The projection 46 is integral with the hub 36 of the spider and is provided at its outer end with a reduced portion 46. The projection 46 spans the space between the hub 36 and the leg 26 and its outer end part 46 is supported in the socket 28. The projection or cutter carrying arbor 46 supports the cutters of the cutting means 12 so that they rotate about a horizontal axis and are located at one side of the vertical axis of the shank 10. A screw 47 may extend through an opening in the leg 26 and be threaded into an opening in the outer end of the projection or arbor 46. The head of the screw 47 may be counter-sunk in a socket 48 in l and 51.

49. From the above description of the spider 11 it will be seen that it is a simple integral member effectively attached to the lower end of the shank in a dependable manner by only four screw threaded parts and with the cutter carrying arbors 41 and 46 cooperating with the sockets in the inner sides of the shank legs to transmit torque or rotational thrusts directly to the shank.

The inner cutting means 12 is in the nature of a roller cutting means and is rotatably carried on the spider projection or arbor 46 to make a round or cylindrical cut in the formation. The construction or formation of the various cutters of the bit and more particularly the cutting parts on teeth of the various cutters are important features of the invention. In the specific form of the invention being described, the inner cut ting means 12 comprises two units or cutters 51. The cutters 51 are annular or substantially cylindrical members and are independently rotatable on the arbors 46. In the particular case illustrated in the drawings, the cutters 51 are rotatably mounted on the arbor 46 through suitable anti-friction roller bearings 52. A spacing washer 53 may be provided between the adjacent ends of the cutters 51. A thrust washer 54 may be welded on the arbor or cutter carrying projections 46 at the outer end of the outermost cutter 51. The inner cutter 51 is adapted to cooperate with the thrust shoulder 55 at the inner end of the arbor 46. The rotatable roller cutters 51 project from the lower end of the cutters 51 of the inner cutting means 12 are accordingly operable to make a round or cylindrical central cut in the formation.

As the intermediate cutter 13, or at least, the cutting parts of the intermediate cutter 13 may be similar to or identical with those of the inner cutters 51, I will proceed with a description of the intermediate cutter 13 in conjunction with a description of the inner cutters 51. The intermediate cutter 13 is rotatable on the horizontal trunnion 49 and projects from the lower end of the shank 10 to make an annular cut in the formation surrounding and joining or adjacent the cut made-by the inner cutters 51. In the particular case illustrated-in the drawings, the intermediate cutter ,13 is rotatably mounted on the trunnion 49 through suitable anti-friction roller bearings 56. A thrust and retaining washer 57 may be welded on the outer end part of the trunnion 49 to retain the cutter 13 on the trunnion. The inner end of the cutter 13 is adapted to engage a vertical annular thrust shoulder 58 at the inner end of thetrimnion 49. The cutter 13 may be similar to or substantially identical with the inner cutters 51 and the cutter 13 and the inner cutters 51 are provided with cutting parts or teeth spaced and related to be particularly effec tive in their action on the formation.

In accordance with the invention, a plurality of circumferential sets or series of cutting teeth are "providedon the periphery of each cutter 13 three'circumferential series, A, B and C, of teeth 59 on each cutter. The teeth 50 of the series A,

and C,--"projec tfrom the peripheries of the v In the typical embodiment of the invention illustrated in the drawings there are The shape of the teeth 59 may be varied somewhat. In the particular case illustrated in the drawings, the teeth 59 are substantially V shaped. The cutters 13 and 51 may be integral members or may be sectional as illustrated in the drawings. As illustrated, the cutters 13 and .51 each comprise three sections, A, B, and C. Each section of the cutters isprovided at its periphery with a series of cutting teeth. The sections A, B, and C' of each cutter may be welded, riveted or otherwise rigidly connected together. In the drawings, I have shown the sections A, B" and C of the cutters connected together by longitudinal rivets 60'.

The cutters in being formed of sections, as just described, are particularly simple and inexpensive of manufacture as the sections A, B and C' may be readily forged or drop forged. The sections A, B and C are comparatively thin and therefore may be satisfactorily drop forged and when formed in this manner have effective teeth 59. The thick or long one-piece roller cutters used heretofore could not be drop forged as the draw necessary in the die prevents the proper shaping of the teeth.

In accordance with the invention, the teeth 59 of the adjacent series A, B and C of each cutterv are staggered or offset circumferentially. Due to the staggering of the teeth of the adjacent series A, B and C of each cutter, the teeth of each series may be spaced substantial distances apart, and the circumferential distances or spaces between the teeth of adjacent series still remain sufllciently short to insure proper rotation of the cutter'through engagement of the teeth with the formation. As the individual teeth of each of the series A, B and C 'are comparatively short, there is a minimum lineal average or total cutting edge engaging the formation at the bottom of the well bore, and therefore a maximum cutting pressure per lineal unit of the cuttingedges 60 "is insured, to provide for the particularly rapid arid effective cutting or penetration of the formation.

It is a feature of the'present invention that the teeth 60 in the series of teeth A, B and C of the sets of cutters 13 and 51 are related or spaced so that they do not track in the cuts in the formation that they have made during a previous rotation of the tool. In accordance with. the invention, the spacing of the teeth 59 of each series A, B and C, is varied or unequal. This relating or unequal spacing of the teeth 59 of each circumferential series of teeth may be carried out in extreme manners, for example, the spaces between the teeth may be graduated or there may be groups of teeth 59 in each series having different spacings. In the specific embodiment of the invention illustrated in the drawings, "each circumferential series A, B and C of teeth has a .group X of teeth 59 that are spaced comparatively close together and a group Y of teeth that are spaced substantial distances apart. The circumferential extents of the groups of teeth X and Y may be unequal or varied, if desired. In the case illustrated in the drawings, the groups of teeth X and Y each extend substantially 180 around the cutter. As described above, the teeth 59 of the adjacent series of teeth are staggered or-offset with relation to one another and to providefor a substantially uniform total active cutting edge, the groups of teeth X and Y of adjacent series may also be pifset to occur at different circumferential zones on the cutters. It is of course, desirable to relate the series of teeth A, B and C so that the closely spaced teeth of the group X of one series is oifset or staggered with relation to the teeth of a widely spaced group Y of an adjacent series. When the teeth 59 of the several series A, B and C are related in this manner, there are no wide toothless portions or gaps in the peripheries of the cutters. It may be preferred to overlap the difierently spaced groups X and Y of teeth of the adjacent series as clearly illus-- trated in Fig. '7 ofthe drawings.

The cutters 13 and 51 provided with the ofiset circumferential series of teeth, each series having groups of teeth 59 of different spacing, are particularly efiective in their action on the for mation as a minimum active lineal cutting edge is provided on each cutter, and the teeth are so spaced about the peripheries of the cutters as to insure proper rotation of the cutters without tracking in previously made cuts.

The outer cutters 14 are provided to ream or cut the Well bore to size and to make an annular cut in the formation, overlapping or adjacent the annular cut made by the intermediate cutter 13. In accordance with the invention, the outer cutters 14 are in the nature of roller cutters rotatable on the projections or arbors 41 of the spider 11. As the arbors 41 are inclined upwardly and outwardly the cutters 14 are rotatable about axes inclined upwardly and outwardly relative to the central axis of the shank. The cutters 14 may be rotatably mounted on the arbors 41 through suitable anti-friction bearings 61. The inner ends of the cutters 14 are adapted to bear against the thrust flanges 42. Thrust collars 62 may be welded on the outer end portions 41 of the arbors 41 at the outer ends of the cutters. The thrust collars 62 may be provided with projecting parts 63 to fit into the sockets 25.

In accordance with the broader aspects of the invention, the cutting parts or teeth of the outer cutting parts 14 may be varied considerably in character. In the form of the invention illustrated in Figs. 1 to 6 of the drawings, each outer cutter 14 is provided with a single circumferentail set or series of spaced teeth 64. The cutters 14 project downwardly and outwardly from the lower end of the shank 10 so that the teeth 64 act on the formation at the bottom of the well bore and the side of the well bore. The outer corners of the teeth 64 may be bevelled as clearly illustrated in Fig. 2.

Figs. 8 and 9 of the drawings illustrate a modified form of cutter 14 that may be employed in place of the cutters 13 or 14 described above, or that may be embodied in the cutting means 12. The cutter 14. illustrated in Figs. 8 and 9 of the drawings is similar generally to a cutter 14, but is provided at its periphery with two sets or series D and E of spaced teeth 65. The teeth 65 of the two series D and E may be equally spaced and may be V shaped as illustrated. The adjacent teeth of the two series D and E are circumferentially staggered or offset. In accordance with this form of the invention, the cutter 14*- is an integral part or member formed of a single piece of material, and the cutters 65 of the series D and E may be formed byinitially providing the cutter with a plurality of equally spaced teeth that extend throughout the length of the cutter. The alternate halves of adjacent teeth are then milled out or otherwise removed to provide the staggered or offset teeth 65 in the two series D and E as illustrated in Figs. 8 and 9. The outer corners 66 of the teeth 65 in the series I) may be bevelled to act as reaming cutting edges.

It is to be noted that in assembling the tool, the inner cutters 51, the intermediate cutter 13 and the outer cutters 14 may be initially assembled on their respective arbors and the retaining outer thrust washers then welded or otherwise secured into place. The assembly of the spider 11 and the several cutters may then be easily and quickly attached to the shank 10 by means of the nut 35 and the screws 43 and 47. The assembly of the one-piece spider and the several cutters of the tool may be handled with ease, and may be easily and quickly applied to and detached from the shank 12. The cutters 13, 14 and 51 may be readily replaced when desired or necessary by detaching the spider 11 from the shank and removing the thrust washers from the outer ends of the cutter carrying arbors or projections.

The invention provides means for flushing the inner cutting means and the outer cutters 14. The lower end of the shank 10 is relieved to receive the upper ends of the cutters 51 as at 67. A circulation passage 68 extends'downwardly in the shank 10 from the chamber 21 to the recess 6'7 which it discharges downwardly against the cutters 51. Recesses 68 are provided in the shank 10 above the outer cutters 14. Vertical passages 69 extend downwardly from the chamber 21 to discharge at the upper end of the recesses 68 and efiectively wash and flush the cutters 14. The enlargement or chamber 21 of the main circulation passage 20 permits the discharge passages 3'7, 68 and 69 to be drilled vertically into the lower end of the shank 10. The discharge from the nut or choke 38 and from the passages 68 and 69 insures the effective washing and flushing of the several cutters and insures the proper circulation at the bottom of the well bore.

It is believed that the operation of the embodiment of the invention illustrated in Figs. 1 to 6 inclusive of the drawings will be readily understood from the foregoing detailed description. In operation the tool is rotated through the drilling string which causes the rotation of the cutters 13, 14 and 51. The cutters 13 and 51, in being rotatable about horizontal axes and in projecting from the lower end of the shank 10, act on the formation at the bottom of the well bore to cut a cylindrical hole with a fiat bottom wall. The independently rotatable cutters 51 of the inner cutting means 12 make a central cylindrical cut in the formation andthe intermediate cutter 13 makes an annular cut around the central cut. The intermediate cutter 13 may be positioned so that its cut is adjacent the periphery of the central cut or joins the central cut. The outer cutters 14 operate to cut the well bore to size and make an annular cut that surrounds and isimmediately adjacent or. joins the cut made by the intermediate cutter 13. The cutting parts or teeth 59 of the intermediate cutter 13 and the inner cutters 51 in being arranged in circumferential series whose teeth are offset or staggered and spaced considerable distances apart, provide for a minimum active cutting edge that insures a maximum pressure per unit of cutting edge so that they are particularly effective and rapid in their cutting action. Further, the teeth 59 of the series A, B and C, in being of different or unequal spacings, cannot track in the previously made cuts. Due tothese features of the present invention, the tool is very efiective and rapid in its operation.

The embodiment of the invention illustrated in Figs. and 11 of the drawings includes generally, a shank '10, a cutter carrying'member or spider '11 detachably mounted on the lower end of the shank '10, a central cutting means 72, and outer cutters '13.

The shank '12 may be substantially identical with the shank 10 described above, that is, it may be an integral member provided with a circulation passage '14 and formed and shaped at its lower end to receive the spider '11 and its cutters. A downwardly projecting pin '15 is provided on the lower end of the shank '10 at a point offset from its vertical axis. The cutter carrying spider '11 is an integral or one piece member provided to carry the cutting members '12 and theouter cutters '13. The spider '11 is provided with an opening '16 for passing the pin '15. An enlargement or socket '17 is provided in the lower end of the opening '16 to receive a nut '18 threaded on the pin '16 to detachably retain the spider '11 on the shank '10. A circulation discharge passage '19 extends downwardly through the shank from the lower end of the passage '14 and discharges from the lower end of the pin '15. A nut '18 is provided at its lower end with a discharge jet or choke for the passage 79.

The spider '11 is provided at its opposite sides with projecting arms 81 having arbors (not shown) for rotatably carrying the outer cutters '13.

The arms 81 and the mountings of theouter cutters '13 may be substantially identical with those of the previously described embodiments.

An internal cutter carrying projection or arbor 82 is provided on the spider 71 to carry the inner cutting means. In accordance with this embodiment of the invention, the arbor 82 is inclined upwardly and outwardly and its outer end engages or is supported-by a downwardly projecting leg 83 on the shank '10. The extreme outer end of the arbor 82 is reduced and fits in a socket 84 in the inner side of the leg 83. Due to the inclination of the arbor 82, the leg 83 may be comparatively cal axis of the shank, or may extend through or across the axis of the shank. In the particular case illustrated in the drawings, thev inner cutting means '12 includes three like cutters independently rotatable on an arbor '12. The cutters 90 may be separated by washers 91 and may be mounted on the arbor '82 through suitable anti-friction bearings 92. The inner cutter 90 bears against the shoulder 85, while a suitable thrust washer 94 is provided between the outer cutter 90 and the inner side of the leg 83. The cutters 90 may be similar to or identical with the cutters 51 described above, that is, they may be provided with a plurality of series of unequally spaced cutting teeth, the teeth of adjacent series being onset. In the particular case illustrated in the drawings, the innermost cutter 90 has its innermost cutting parts at substantially the vertical center of the tool. Due to this positioning of the cutting means '12, the cutters 90 act on the formation at only one side of the axis of the shank. The cutter carrying arbor 82 is spaced substantially 90 from the cutter carrying arbors of the outer cutters '13, and is diametrically opposite the pin '15.

The outer cutters '13 are rotatably mounted on the outer ends of the arms 81 to rotate about upwardly and outwardly inclined axes, and operate to ream the well bore and make an annular cut in the formation joining the central cut made by the inner cutting means '12. The outer cutters '13 may be similar to the cutters 14 or the cutters 14' described above. In the particular case illustrated in the drawings, the cutters '13 are similar to the cutters 14, each having a single series of cutting teeth 98.

The form of the invention illustrated in Figs. 10 and 11 of the drawings is simple and inexpensive of manufacture and may be quickly and easily assembled. The spider 11 carrying the cutters '13 and 90 may be easily and quickly detached from the shank '10'as a unit. The inner cutters 90 are effective in making a central cut in the formation, while the outer cutters '13 cut the well bore to size and make an annular cut joining or adjacent the central inner cut.

Having described only typical forms and applications of the invention, we do not wish to limit ourselves to the specific details set forth, but wish to reserve .to ourselves any changes or variations that may appearto those skilled in the art or that fall within the scope of the following claims.

Having described our invention, we claim:

1. In a well bit, a shank having a downwardly facing lower end face; a pin projecting downwardly from the. lower end of the face, there being a fluid passage in the shank discharging through the pin, a cutter carrying spider, and a member on the pin detachably retaining the spider on the shank in engagement with the lower end face of the shank.

2. In a well bit, a shank having a depending pin on its lower end, there being a fluid passage in the shank discharging from the pin, a cutter carrying spider, and a member on the pin de-v tachably retaining the spider on the shank, the said member forming a nozzle for the discharge of the fluid passage.

3. A roller cutter for use on a well toolincluding a body to be rotatably mounted on the tool, and having a plurality-of circumferential series of spaced teeth on the body, each series including groups of teeth, the teeth of different groups having different pitch, the teeth of adjacent series being circumferentially offset.

4. A well bit including a shank, a spider at the lower end of the shank, a plurality of roller cutters on the spider, one-cutter having its end at or intersecting the central'vertical axis of the shank, and means for detachably securing the spider to the lower end of the shank -including a downwardly projecting pin on the lower end of the shank offset from the central vertical axis of the shank, there being an opening in the spider to receive the pin, and a removable retaining member on the pin clamping the spider against the lower end of the shank. I

5. A well bit including a shank having-substantially diametrically opposite legs projecting from its lower end and a third downwardly projecting leg spaced from the first mentioned legs, a cutter mounting member detachably mounted on the make an annular cut in the formation, and a cutter rotatable on the other inclined part and operable to make a central cut in the formation.

6. A well bit including a shank having substantially diametrically opposite legs projecting from its lower end and a third downwardly pm jecting leg spaced from the first mentioned legs; a cutter mounting member detachably mounted on the lower end of the shank and having inclined projecting parts whose outer ends bear on the first mentioned legs, and an inclined part bearing on the third leg, cutters rotatable on the said parts, and means discharging fluid from the lower end of the shank at a point opposite said third leg.

7. A well bit including a shank having substantially diametrically opposite legs projecting from its lower end and a third downwardly projecting leg spaced from the first mentioned legs, a cutter mounting member detachably mounted on the lower end of the shank and having upwardly and outwardly inclined parts whose ends bear on the first mentioned legs and having an upwardly and outwardly inclined part bearing on the third leg, and cutters rotatable on the said inclined parts.

8. A well bit including, a body, a plurality of legs projecting from the lower end of the body, there being sockets in the inner sides of the legs and openings in the legs communicating with the sockets, a mounting member having projecting parts whose outer ends bear against the walls of the sockets and having registering with the openings in the legs, cutters rotatable on the said parts, and threaded members passing through the openings in the legs and into openings in the said parts to attach the member to the body and to tie the legs together by the member.

9. A well bit including, a body, a plurality of legs projecting from the lower end of the body having downwardly and outwardly inclined inner faces, there being sockets in the inner sides of the legs, a mounting member having upwardly and outwardly projecting parts whose outer ends bear outwardly on the walls of the sockets and whose sesame outer end portions bear upwardly against the upper walls of the sockets, rotatable cutters on said parts, and means removably attaching the member to the body. 10. A well bit including, a body, a plurality of legs projecting from the lower end of the body the legs having downwardly and outwardly inclined inner faces, there being sockets in the inher sides of the legs, a mounting member having upwardly and outwardly projecting parts whose outer ends bear outwardly on the walls of the sockets and whose outer end portions bear upwardly against the upper walls of the sockets, rotatable cutters on said parts, and means removably attaching the member to the body, the sockets extending downwardly to and being open at the lower ends of the legs.

11. A well drilling bit including a body, inner and outer cutters, means mounting the inner cutter at the lower end of the body to make a cylindrical cut in the formation and mounting the outer cutter at the lower end of the body to make an annular cut in the formation, the inner cutter being substantially horizontally disposed and being in the form of a unitary roller of substantially uniform diameter and having a plurality of circumferential series of teeth each series including a plurality of groups of teeth, the teeth of each group being of different pitch, and the series of teeth being related so that the teeth of adjacent series are circumferentially offset.

12. A well bit including, a body having a. leg projecting downwardly from its lower portion, there being a socket in the inner side of the leg and an opening through the leg communicating with the socket, a cutter mounting member at the lower end of the body and having a reduced projecting part with its outer end bearing in the socket and having an opening registering with the opening in the leg, a cutter rotatable on said part, and a threaded member extending through the opening in the leg and into the opening in said part to hold said part tight'in the socket.

JOHN H. HOWARD. ALFRED C. CATLAND. 

